Comets to Mars?

In _Entering Space_ Robert Zubrin mentions that it would take only a
small amount of Delta V to send Kuiper Belt Objects down to Mars. He
believes comets striking Mars would thicken the atmosphere and raise the
temperature. (I also seem to recall Kim Stanley Robinson using this idea
in his Mars trilogy)

But now in John S. Lewis' _Rain of Iron and Ice_ I read about
atmospheric erosion by meteorites. Most the atmosphere the other side
of a tangent plane touching the Martian sphere at point of impact is
sent into space.

So would comets add or subtract to Mars' atmosphere?

By my calculations KBOs sent on a Hohmann transfer orbit to Mars would
come into Mars orbit at about 9 km/sec. Mars gravity would add another
5. So I believe a KBO would hit Mars at around 14 km/sec.

--
Hop David
http://clowder.net/hop/index.html

On Mon, 10 Nov 2003 12:01:58 -0700
Hop David wrote:

In _Entering Space_ Robert Zubrin mentions that it would take only a
small amount of Delta V to send Kuiper Belt Objects down to Mars. He
believes comets striking Mars would thicken the atmosphere and raise the
temperature. (I also seem to recall Kim Stanley Robinson using this idea
in his Mars trilogy)

But now in John S. Lewis' _Rain of Iron and Ice_ I read about
atmospheric erosion by meteorites. Most the atmosphere the other side
of a tangent plane touching the Martian sphere at point of impact is
sent into space.

So would comets add or subtract to Mars' atmosphere?

By my calculations KBOs sent on a Hohmann transfer orbit to Mars would
come into Mars orbit at about 9 km/sec. Mars gravity would add another
5. So I believe a KBO would hit Mars at around 14 km/sec.

If the impact is vertical then most of the momentum of the impacting object would be absorbed by the martian crust. If the impact is off vertical then more of the momentum would go into the atmosphere but I suspect would be transferred over the whole trajectory of the object.

I doubt that the mass lost from the atmosphere would be anywhere near as much as delivered by the impacting body.
----
Michael Smith
Mail address and GPG key available from www.netapps.com.au

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Michael Smith wrote:
On Mon, 10 Nov 2003 12:01:58 -0700
Hop David wrote:


In _Entering Space_ Robert Zubrin mentions that it would take only a
small amount of Delta V to send Kuiper Belt Objects down to Mars. He
believes comets striking Mars would thicken the atmosphere and raise the
temperature. (I also seem to recall Kim Stanley Robinson using this idea
in his Mars trilogy)

But now in John S. Lewis' _Rain of Iron and Ice_ I read about
atmospheric erosion by meteorites. Most the atmosphere the other side
of a tangent plane touching the Martian sphere at point of impact is
sent into space.

So would comets add or subtract to Mars' atmosphere?

By my calculations KBOs sent on a Hohmann transfer orbit to Mars would
come into Mars orbit at about 9 km/sec. Mars gravity would add another
5. So I believe a KBO would hit Mars at around 14 km/sec.


If the impact is vertical then most of the momentum of the impacting
object would be absorbed by the martian crust. If the impact is off vertical
then more of the momentum would go into the atmosphere but I suspect would
be transferred over the whole trajectory of the object.

So a hit smack dab in middle leaves more mass than grazing a limb?


I doubt that the mass lost from the atmosphere would be anywhere near as much
as delivered by the impacting body.

Is this true regardless of velocity? I guess atmospheric erosion is
caused by stoney or metallic meteorites that don't replace ejected
atmosphere with gas of their own.

If high velocity did cause a net loss maybe pelting Mars with Trojan
snowballs would be better than KBOs.

----
Michael Smith
Mail address and GPG key available from www.netapps.com.au


--
Hop David
http://clowder.net/hop/index.html

In message
Hop David wrote:

By my calculations KBOs sent on a Hohmann transfer orbit to Mars would
come into Mars orbit at about 9 km/sec. Mars gravity would add another
5. So I believe a KBO would hit Mars at around 14 km/sec.

I've wondered what the effect would be of putting pairs of ice bodies
into close flyby trajectories either side of Mars, aimed so they
collide. Say aim one over the north pole, one over the south and get a
big bang over the equator. Hopefully you get a big cloud of steam with
insufficient velocity to stay up...

Anthony

--
| Weather prediction will never be accurate until we |
| kill all the butterflies |

Anthony Frost wrote in message ...
In message
Hop David wrote:

By my calculations KBOs sent on a Hohmann transfer orbit to Mars would
come into Mars orbit at about 9 km/sec. Mars gravity would add another
5. So I believe a KBO would hit Mars at around 14 km/sec.

I've wondered what the effect would be of putting pairs of ice bodies
into close flyby trajectories either side of Mars, aimed so they
collide. Say aim one over the north pole, one over the south and get a
big bang over the equator. Hopefully you get a big cloud of steam with
insufficient velocity to stay up...

Anthony

I'd rather put them into retrograde resp. direct orbit, then scatter
them into two opposing accretion discs.

Regards

Carsten Nielsen
Denmark

Anthony Frost wrote:
In message
Hop David wrote:

By my calculations KBOs sent on a Hohmann transfer orbit to Mars would
come into Mars orbit at about 9 km/sec. Mars gravity would add another
5. So I believe a KBO would hit Mars at around 14 km/sec.

I've wondered what the effect would be of putting pairs of ice bodies
into close flyby trajectories either side of Mars, aimed so they
collide. Say aim one over the north pole, one over the south and get a
big bang over the equator. Hopefully you get a big cloud of steam with
insufficient velocity to stay up...

Anthony



Or maybe smack Deimos to bring it down to Mars synchronous and Phobos to
bring it to the surface. Those might be first steps to building a
Martian bean stalk. If Phobos and Deimos are piles of rubble, the
collisions might result in huge clouds of debris that would be a
nuisance for some time to come.

--
Hop David
http://clowder.net/hop/index.html

On Mon, 10 Nov 2003, Hop David wrote:
|But now in John S. Lewis' _Rain of Iron and Ice_ I read about
|atmospheric erosion by meteorites.

Hmm.. I think I'll check out http://www.amazon.com and see if
it is available there.

|Most the atmosphere the other side of a tangent plane touching the
|Martian sphere at point of impact is sent into space.

Is the atmosphere permanently lost, or does it eventually come
back down? I'd think that loss of atmosphere is something that
is undesirable; does this still happen if the meterorites are
broken up (with nuclear bombs, so they become fragmentary or
shatter) before they enter Mars' atmosphere?

|So would comets add or subtract to Mars' atmosphere?

How much mass can you count on coming from those comets that you can
locate and drive to the near vicinity of Mars? Don't you lose some
of that mass, just driving the comets into Mars's orbit?

|By my calculations KBOs sent on a Hohmann transfer orbit to Mars
|would come into Mars orbit at about 9 km/sec. Mars gravity would add
|another 5. So I believe a KBO would hit Mars at around 14 km/sec.

If you don't first break the meteorites up before entry, you are
going to get a lot more surface material mixed into the atmosphere,
but if you can successfully break them up first, the atmosphere
itself is going to be the only thing to slow down the meteorites'
entry.

On Mon, 10 Nov 2003 12:01:58 -0700, Hop David
wrote:

In _Entering Space_ Robert Zubrin mentions that it would take only a
small amount of Delta V to send Kuiper Belt Objects down to Mars. He
believes comets striking Mars would thicken the atmosphere and raise the
temperature. (I also seem to recall Kim Stanley Robinson using this idea
in his Mars trilogy)

But now in John S. Lewis' _Rain of Iron and Ice_ I read about
atmospheric erosion by meteorites. Most the atmosphere the other side
of a tangent plane touching the Martian sphere at point of impact is
sent into space.

So would comets add or subtract to Mars' atmosphere?

Depends on their size and impact velocity.

By my calculations KBOs sent on a Hohmann transfer orbit to Mars would
come into Mars orbit at about 9 km/sec. Mars gravity would add another
5. So I believe a KBO would hit Mars at around 14 km/sec.

It would be easy to avoid the atmosphere losses and large-scale
areophysical effects resulting from a straight-in impact of a large
body by arranging a suitable pre-impact with a much smaller body to
disrupt the main incoming body. Such a pre-impact would convert the
incoming into an expanding sphere of rapidly declining average
density, spreading the impact out over an entire hemisphere and a much
longer period of time. Even objects as large as peta-ton class could
probably be "soft-landed" on Mars using this technique, avoiding the
significant atmosphere losses and awkward long-term areophysical
consequences of large straight-in impacts.

-- Roy L